[libc] ensure tls dtors are called in main thread

Author: SchrodingerZhu

libc/src/stdlib/CMakeLists.txt

@@ -598,6 +598,7 @@ add_entrypoint_object(
   CXX_STANDARD
     20 # For constinit
   DEPENDS
+    libc.src.__support.threads.thread
     .exit_handler
 )
 

libc/src/stdlib/atexit.cpp

@@ -10,6 +10,7 @@
 #include "hdr/types/atexithandler_t.h"
 #include "src/__support/common.h"
 #include "src/__support/macros/config.h"
+#include "src/__support/threads/thread.h"
 #include "src/stdlib/exit_handler.h"
 
 namespace LIBC_NAMESPACE_DECL {
@@ -26,6 +27,7 @@ int __cxa_atexit(AtExitCallback *callback, void *payload, void *) {
 
 void __cxa_finalize(void *dso) {
   if (!dso) {
+    internal::call_atexit_callbacks(self.attrib);
     call_exit_callbacks(atexit_callbacks);
     if (teardown_main_tls)
       teardown_main_tls();

libc/test/integration/src/__support/threads/CMakeLists.txt

@@ -25,3 +25,13 @@ add_integration_test(
   DEPENDS
     libc.src.__support.threads.thread
 )
+
+add_integration_test(
+  main_exit_test
+  SUITE
+    libc-support-threads-integration-tests
+  SRCS
+    main_exit_test.cpp
+  DEPENDS
+    libc.src.__support.threads.thread
+)

libc/test/integration/src/__support/threads/main_exit_test.cpp

@@ -0,0 +1,31 @@
+//===-- Test handling of thread local data --------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/threads/thread.h"
+#include "test/IntegrationTest/test.h"
+
+bool called = false;
+
+extern "C" {
+[[gnu::weak]]
+void *__dso_handle = nullptr;
+
+int __cxa_thread_atexit_impl(void (*func)(void *), void *arg, void *dso);
+}
+
+[[gnu::destructor]]
+void destructor() {
+  if (!called)
+    __builtin_trap();
+}
+
+TEST_MAIN() {
+  __cxa_thread_atexit_impl([](void *) { called = true; }, nullptr,
+                           __dso_handle);
+  return 0;
+}